Line pressure control apparatus and line pressure control method for automatic transmission

Abstract

An ECU executes a program that includes the steps of setting a line pressure to a line pressure ( 1 ) that is appropriate for improving fuel efficiency, if an automatic transmission is not shifting, and a deceleration slip control for a lock-up clutch is not being executed; setting the line pressure to a line pressure ( 2 ) that is equal to or lower than a line pressure ( 3 ) that is appropriate when the automatic transmission is shifting, if it is determined that the automatic transmission is not shifting, and the deceleration slip control is being executed; and setting the line pressure to the line pressure ( 3 ), if it is determined that the automatic transmission is shifting. The line pressure ( 1 ) is lower than the line pressure ( 2 ). The line pressure ( 2 ) is equal to or lower than the line pressure ( 3 ).

1. A line pressure control apparatus for an automatic transmission that includes a lock-up clutch, comprising:
 a first determination device that determines whether the automatic transmission is shifting; 
 a second determination device that determines whether a slip control for the lock-up clutch is being executed while a vehicle is decelerated by releasing an accelerator pedal; and 
 a setting device that sets a line pressure to a first value that is higher than a second value if the first determination device determines that the automatic transmission is shifting, wherein the setting device sets the line pressure to the second value if the first determination device determines that the automatic transmission is not shifting, and the second determination device determines that the slip control is not being executed while the vehicle is decelerated by releasing the accelerator pedal, and the setting device sets the line pressure to a value higher than the second value if the first determination device determines that the automatic transmission is not shifting, and the second determination device determines that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal. 
 
   
   
     2. The line pressure control apparatus for the automatic transmission according to  claim 1 , wherein the setting device includes a device that sets the line pressure to a value that is higher than the second value and is lower than the first value if the first determination device determines that the automatic transmission is not shifting, and the second determination device determines that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal. 
   
   
     3. The line pressure control apparatus for the automatic transmission according to  claim 1 , wherein the setting device sets the first value to a value that is appropriate when the automatic transmission is shifting, and the setting device sets the second value to a value that is appropriate for improving fuel efficiency. 
   
   
     4. The line pressure control apparatus for the automatic transmission according to  claim 3 , wherein if the first determination device determines that the automatic transmission is not shifting, and the second determination device determines that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal, the setting device sets the line pressure to a value that is equal to or lower than the value that is appropriate when the automatic transmission is shifting. 
   
   
     5. The line pressure control apparatus for the automatic transmission according to  claim 3 , wherein if the first determination device determines that the automatic transmission is not shifting, and the second determination device determines that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal, the setting device sets the line pressure to the first value. 
   
   
     6. The line pressure control apparatus for the automatic transmission according to  claim 3 , wherein if the first determination device determines that the automatic transmission is not shifting, and the second determination device determines that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal, the setting device sets the line pressure to a value at which the lock-up clutch is not engaged when the automatic transmission starts to shift while the slip control is being executed. 
   
   
     7. A line pressure control method for an automatic transmission that includes a lock-up clutch, comprising the steps of:
 determining whether the automatic transmission is shifting; 
 determining whether a slip control for the lock-up clutch is being executed while a vehicle is decelerated by releasing an accelerator pedal; 
 setting a line pressure to a first value that is higher than a second value if it is determined that the automatic transmission is shifting; 
 setting the line pressure to the second value if it is determined that the automatic transmission is not shifting, and it is determined that the slip control is not being executed while the vehicle is decelerated by releasing the accelerator pedal; and 
 setting the line pressure to a value that is higher than the second value if it is determined that the automatic transmission is not shifting, and it is determined that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal. 
 
   
   
     8. The line pressure control method for the automatic transmission according to  claim 7 , wherein the line pressure is set to a value that is higher than the second value and is lower than the first value if it is determined that the automatic transmission is not shifting, and it is determined that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal. 
   
   
     9. The line pressure control method for the automatic transmission according to  claim 7 , wherein the first value is set to a value that is appropriate when the automatic transmission is shifting, and the second value is set to a value that is appropriate for improving fuel efficiency. 
   
   
     10. The line pressure control method for the automatic transmission according to  claim 9 , wherein if it is determined that the automatic transmission is not shifting, and it is determined that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal, the line pressure is set to a value that equal to or lower than the value that is appropriate when the automatic transmission is shifting. 
   
   
     11. The line pressure control method for the automatic transmission according to  claim 9 , wherein if it is determined that the automatic transmission is not shifting, and it is determined that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal, the line pressure is set to the first value. 
   
   
     12. The line pressure control method for the automatic transmission according to  claim 9 , wherein if it is determined that the automatic transmission is not shifting, and it is determined that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal, the line pressure is set to a value at which the lock-up clutch is not engaged when the automatic transmission starts to shift while the slip control is being executed. 
   
   
     13. A line pressure control apparatus for an automatic transmission that includes a lock-up clutch, comprising:
 first determination means for determining whether the automatic transmission is shifting; 
 second determination means for determining whether a slip control for the lock-up clutch is being executed while a vehicle is decelerated by releasing an accelerator pedal; and 
 setting means for setting a line pressure to a first value that is higher than a second value if the first determination means determines that the automatic transmission is shifting, wherein the setting means sets the line pressure to the second value if the first determination means determines that the automatic transmission is not shifting, and the second determination means determines that the slip control is not being executed while the vehicle is decelerated by releasing the accelerator pedal, and the setting means sets the line pressure to a value higher than the second value if the first determination means determines that the automatic transmission is not shifting, and the second determination means determines that the slip control is being executed while the vehicle is decelerated by releasing the accelerator pedal.